This disclosure is directed to an improved method of manufacturing a current collector/catalyst electrode/membrane assembly which has increased electrical conductivity in the area between the catalyst electrode and the current collector. Such assemblies are useful in a variety of applications including, for example, fuel cells, water electrolysis cells, chlor-alkali cells, and the like. The assembly produced according to the present invention is substantially structurally stable which allows the membrane portion to be substantially thinner than those presently available, and reduces the ionic resistance of the membrane.
It is highly desirable in most uses, given the harsh conditions of many of the applications for the membrane, that the membrane portion of the assembly have substantial structural integrity. Thinner membranes have been viewed as fragile and yet thinner membranes are desirable to reduce ionic resistance. This requires a balance between providing adequate structural support for the assembly on the one hand and yet reducing the membrane's thickness to reduce ionic resistance without it's sacrificing structural integrity.
References which have a bearing on this invention include Pat. No. 4,272,353 which discloses a surface abrading technique for scratching a solid polymer electrolyte (SPE) base member in preparation for subsequent treatment. U.S. Pat. No. 4,272,560 describes a membrane having a cathode made of multiple coatings with a backing fabric. A dissolved copolymer is used in fabrication of this electrode. U.S. Pat. No. 4,182,670 sets forth a combined cathode and diaphragm utilizing a spray coating of a metal substrate with powdered metal. A polymer impregnated diaphragm is also described. An electrode body having impregnated powdered metal (typically noble metals) is set forth in U.S. Pat. No. 3,276,911. It also mentioned a permeable ionic electrolytic material. U.S. Pat. No. 4,364,813 discloses catalytic particles deposited on an ion exchange material with a SPE membrane. This patent has an ion exchange feature mentioning a sulfonic group. U.S. Pat. No. 4,366,041 describes a cathode and diaphragm assembly with a sacrificial film made of wax.
The present disclosure describes a structurally stable electrode assembly which has lower ionic resistance in the membrane portion and which has higher electrical conductivity in the catalyst electrode and current collector portions. Thinness is achieved without sacrifice of structural integrity and yet resistance to ionic movement through the membrane is reduced.
While the foregoing refers in general terms to the present assembly, the structure thereof and the method of manufacture are exemplified in the detailed description of the preferred embodiments following.